To increase the output and efficiency of motor vehicle air-conditioning systems, air-conditioning system-internal heat exchangers, so-called internal heat exchangers (IHX) are known, which thermally couple a section of the refrigerant circuit running between evaporator and compressor to a section of the refrigerant circuit running between condenser and expansion valve. In this way, the relatively cold refrigerant flowing from the evaporator to the compressor can be employed for pre-cooling or super-cooling of the comparatively warm refrigerant fed to the expansion device on the high-pressure side of the refrigerant circuit.
For optimizing the mode of operation of such heat exchangers in the refrigerant circuit, the geometrical dimensions and shapes of the tubes are important. In an existing vehicle package, which hardly offers any room for the individual adaptation or changing of the outer contour or outer geometry of the heat exchanger, it is relatively difficult to adapt such heat exchangers to given requirements individually, for example vehicle type-specifically, with regard to their heat exchanger capacity.
Internal heat exchangers can furthermore be designed as coaxial tube heat exchangers. Here, at least one inner tube is completely enclosed by an outer tube in circumferential direction. In the interior space of the inner tube and in the intermediate space between inner and outer tube, an exchange of thermal energy between the heat exchanger medium which in each case flows in the opposite flow direction can then take place. For connecting coaxial tube heat exchangers into the refrigerant circuit of an air-conditioning system it is necessary to lead the inner tube through the outer tube or provide a suitable connection for the outer tube surrounding the inner tube.
EP 1 101 638 A1, for example, describes a tube arrangement with at least one connector. The connector in this case has a cylindrical shape with a cavity and a first passage through a first longitudinal end. The inner tube in this case extends through the first passage and through the cavity. The connector furthermore contains a radially expanded opening at an end of the cavity in order to receive an outer tube. Here, the outer tube is connected to the connector via a press fit.
Providing a separate connector on the one hand increases the number of components for an internal heat exchanger. On the other hand, the manufacturing and assembly process for such connection solutions becomes comparatively complex. Since the tubes during the operation of the heat exchanger later on are supplied with a pressurized heat exchanger medium, a fluid-tight, pressure-stable and durable connection of the individual components has to be ensured.
In view of the foregoing, at least one object is to provide an improved internal heat exchanger for a motor vehicle air-conditioning system that can be produced particularly efficiently, cost-effectively and simply. At least another object is to provide a component reduction and by a possible weight minimization and a long lifespan as well as a good thermal load capacity. In addition, other objects, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.